U.S. patent number 5,249,950 [Application Number 07/828,031] was granted by the patent office on 1993-10-05 for heated stripper shoe assembly.
This patent grant is currently assigned to Block Systems Inc.. Invention is credited to Michael E. Woolford.
United States Patent |
5,249,950 |
Woolford |
October 5, 1993 |
**Please see images for:
( Reexamination Certificate ) ** |
Heated stripper shoe assembly
Abstract
The invention is a heated stripper shoe assembly for use in
manufacture of concrete masonry blocks. The heated stripper shoe
has a stripper shoe plate, at least one heat blocks and at least
one heat element fitted within the heat block. Optionally, the
stripper shoe assembly may also include a heat shroud positioned
over the heat block on the upper surface of the stripper shoe
plate, a standoff attached to the heat shroud for affixing the
assembly to a block machine, and a mold for use with the stripper
shoe assembly. The invention also includes methods of using the
assembly.
Inventors: |
Woolford; Michael E. (Lake
Elmo, MN) |
Assignee: |
Block Systems Inc. (North St.
Paul, MN)
|
Family
ID: |
25250759 |
Appl.
No.: |
07/828,031 |
Filed: |
January 30, 1992 |
Current U.S.
Class: |
425/412; 100/218;
425/413; 425/422; 425/443; 425/444 |
Current CPC
Class: |
B28B
7/42 (20130101); B28B 3/021 (20130101) |
Current International
Class: |
B28B
7/40 (20060101); B28B 7/40 (20060101); B28B
7/42 (20060101); B28B 7/42 (20060101); B28B
3/02 (20060101); B28B 3/02 (20060101); B28B
013/06 () |
Field of
Search: |
;249/66.1,74,78,136
;425/253,255,407,412,413,422,436R,443,444,452,DIG.13
;100/218,93R,93P |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1188116 |
|
Jun 1985 |
|
CA |
|
1811932 |
|
Jun 1978 |
|
DE |
|
2755833 |
|
Jul 1988 |
|
DE |
|
1385207 |
|
Feb 1975 |
|
GB |
|
2213095 |
|
Aug 1989 |
|
GB |
|
Other References
Handy Stone Retaining Wall System Literature, 1989. .
Standard Load-Bearing Wall Tile Literature, 1924. .
Aztech Wall System Technical Specification, 1989. .
Vulcan Cartridge Heater Specification, W. W. Granger Catalog (no
date). .
Steel ASTM Ratings, 1977. .
Diamond Wall System, Design Manual, 1989. .
Anchor Autoclave Product Literature, 1990..
|
Primary Examiner: Heitbrink; Tim
Assistant Examiner: Mackey; James P.
Attorney, Agent or Firm: Merchant, Gould, Smith, Edell,
Welter & Schmidt
Claims
I claim as my invention:
1. A heated stripper shoe assembly comprising means for forming
structural features on composite masonry blocks, said forming means
comprising:
(a) a stripper shoe plate having a top side and a bottom side, said
stripper shoe plate bottom side comprising at least one
indentation;
(b) means for applying heat to selected areas of the plate, said
heating applying means comprising a heating element affixed to the
top side of said plate, and
(c) means for fastening said heating element to said stripper shoe
plate top side, said fastening means positioned on said stripper
shoe plate top side adjacent the indentation in said plate bottom
side, said heating element positioned within said fastening
means.
2. The assembly of claim 1 wherein said stripper shoe plate
comprises at least four edges, and said stripper shoe plate
indentation comprises a depression running the length of at least
one edge of the shoe plate, and said heating element is positioned
on the top side of said stripper shoe plate parallel to said
indentation.
3. The assembly of claim 2 wherein said fastening means comprises a
hollow rectangular block having a top side and a bottom side, and
said hollow rectangular block is positioned parallel to said
indentation.
4. The assembly of claim 3 wherein said block bottom side is open
and said heating element is in contact with said stripper shoe
plate top side.
5. The assembly of claim 3 wherein said heating element comprises
an electrical resistance element removably inserted into said
hollow rectangular block.
6. The assembly of claim 3 additionally comprising a heat shroud,
said heat shroud positioned on said heated stripper shoe plate top
side, said shroud having an indentation for enclosing said hollow
rectangular block.
7. The assembly of claim 3 wherein said hollow rectangular block
comprises a metal alloy.
8. The assembly of claim 7 wherein said hollow rectangular block
metal alloy is selected from the group consisting of ASTM A36
steel, ASTM 41-40 carbon steel, and mixtures thereof.
9. The assembly of claim 7 wherein said hollow rectangular block
metal alloy comprises ASTM A36 steel.
10. The assembly of claim 6 wherein said heat shroud comprises a
metal compound selected from the group consisting of copper, brass,
elemental aluminum, an aluminum oxide, an aluminum alloy, and
mixtures thereof.
11. The assembly of claim 10 wherein said heat shroud comprises
elemental aluminum.
12. The assembly of claim 1 wherein said heated stripper shoe
assembly additionally comprises a heat shroud and a standoff, said
standoff affixed to said heat shroud and said heat shroud affixed
to said heated stripper shoe plate top side.
13. A heated stripper shoe assembly for use in manufacture of
concrete masonry block, said heated stripper shoe assembly
comprising means for forming structural features on composite
masonry block, said forming means comprising:
(a) a stripper shoe plate comprising a lower side, a top side and
first, second, third and fourth edges, said stripper shoe plate
having first and second indentations located adjacent and
substantially parallel to respective first and second edges on the
plate wherein said first edge is parallel to said second edge
across the surface of said stripper shoe plate;
(b) at least two heat blocks, including a first heat block and a
second heat block, said first heat block positioned on said
stripper shoe plate top side parallel and adjacent to said first
indentation, said second heat block positioned on said stripper
shoe plate top side substantially parallel and adjacent to said
second indentation, said first and second heat blocks each
comprising a hollow rectangular block having a top side and a
bottom side, said block bottom side having an opening;
(c) at least two heating elements, including a first heating
element and a second heating element, said first and second heating
elements each comprising a cylinder, said first element removably
inserted within said first heat block, and said second element
removably inserted into said second heat block wherein each of said
heat block bottom side openings allows free transmission of heat to
said stripper shoe plate top side while insulating said stripper
shoe assembly from heat generated by each of said heating
elements;
(d) a heat shroud positioned over said heat blocks on the top side
of said stripper shoe plate, said heat shroud comprising a lower
side and an upper side, said heat shroud lower side having at least
two heat shroud indentations for enclosing said first and second
heat blocks, and
(e) means for attaching said heated stripper shoe assembly to a
block machine, said attachment means comprising a standoff attached
to said heat shroud.
14. The assembly of claim 13 wherein said first and second heat
blocks each comprise a metal alloy selected from the group
consisting of ASTM A36 steel, ASTM 41-40 carbon steel, and mixtures
thereof.
15. The assembly of claim 13 wherein said first and second heating
elements each comprise an electrical resistance element having a
wattage ranging from about 450 to about 1500 watts.
16. The assembly of claim 13 additionally comprising a mold
comprising four sides designed and positioned in a manner to
complement the outer perimeter of the stripper shoe plate, said
mold comprising an open bottom and open top.
17. The assembly of claim 16 wherein said first and second heating
elements comprise electrical resistance elements having a wattage
ranging from about 450 to about 1500 watts.
18. The assembly of claim 16 wherein said heat shroud comprises an
aluminum alloy and said standoff comprises steel.
Description
FIELD OF THE INVENTION
The invention relates generally to stripper shoe/mold assemblies
for the manufacture of concrete masonry blocks. More specifically,
the invention relates to heated stripper shoe/mold assemblies for
the molding of concrete blocks having edges or other detail or
ornamentation of varying size.
BACKGROUND OF THE INVENTION
Various devices have been developed for the automatic manufacture
of concrete masonry blocks. For example, Bernham et al, U.S. Pat.
No. 4,214,655, disclose a machine for the automated casting,
curing, moving and stacking of concrete blocks. Jenkins, U.S. Pat.
No. 4,132,492, discloses a self-propelled concrete screed machine
having a winch and cable propulsion system.
Whissell, U.S. Pat. No. 4,802,836, discloses a compaction device
for concrete block molding. Pardo, U.S. Pat. No. 4,909,717 and
counterpart UK Patent Application No. 2,213,095A, discloses a
concrete masonry casting apparatus incorporating reciprocal
actuating plungers which cause a shape modification of blocks
during casting.
However, automated block molding processes often cannot provide
blocks of varying size with a high level of detail or ornamentation
having the required structural integrity. For example, wet concrete
fill used in the manufacture of blocks often transfers moisture to
the stripper shoe during the process of compaction. Once wet, the
stripper shoe becomes sticky due to the moisture present at its
surface. As a consequence, fill material may stick to the stripper
shoe.
The shoe may become fouled with mix, especially in indented areas
used to form ornamentation, design, or detail on the blocks. In
turn, various intended features of the block may be malformed or
completely omitted as indentations or patterning on the stripper
shoe are clogged or fouled with concrete mix. Ultimately this
results in block features which are malformed and further eroded
during curing and use. This problem fails to lend itself to the
efficient manufacture of blocks having the required structural
integrity and the intended level of detail or ornamentation.
However, in overcoming the problem of stripper shoe fouling,
several requirements of automated manufacture must be satisfied.
The elements of the block molding machine must withstand automated
block molding processes which often involve a high degree of
vibration, dirt, and compression, among other environmental
stresses. Electrical elements are often not capable of surviving
over a long term period under these conditions. Further, head
assemblies must be serviceable to provide for operator safety as
well as easy disassembly.
As a result, a need exists for a non-fouling stripper shoe and
stripper shoe/mold assembly allowing for the formation of concrete
masonry blocks of a high level of detail which at the same time
provides for easy serviceability, operator safety, and longevity in
an environment of high manufacturing stress.
SUMMARY OF THE INVENTION
In accordance with the invention there is provided a heated
stripper shoe comprising a stripper shoe plate, and at least one
removable heat element positioned within the heat block.
In accordance with another aspect of the invention there is
provided a heated stripper shoe and mold assembly for the
manufacture of composite masonry blocks comprising a stripper shoe
plate, a heat block positioned on the heated stripper shoe, a heat
element inserted within the heat block, a heat shroud positioned
over the heat block, means for attaching the heated stripper shoe
to the block machine head, and a mold.
In accordance with a further aspect of the invention there is
provided a method of using the shoe and mold assembly disclosed
herein.
I have found that by applying heat, through the stripper shoe, to
the concrete fill adjacent the desired feature or the point of
detail or ornamentation, the fill dries and hardens quickly. The
fill does not adhere to and foul the stripper shoe lower surface.
Heat transmitted from the heat elements through the shoe contacts
the fill during compression and evaporates excess water from the
surface of the fill. Heat prevents moisture from forming on the
lower surface of the shoe and, in turn, dissipates any opportunity
for an adhesive effect between the shoe and each subsequent batch
of fill or mix.
The invention allows for molding blocks of all sizes, having high
levels of detail, without fouling the stripper shoe or malforming
the block or block feature. Through use of the invention, blocks
having features of minimal size can be formed with high precision
and structural integrity.
In its preferred mode the invention incorporates a stripper shoe
which has a heat element, detachably mounted to the shoe upper
side, adjacent the indentation in the shoe lower side. The design
of the invention withstands environmental stresses such as
vibration, dirt, and compression and offers a system which is
easily disassembled for repair or modification without risk to the
operation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of the heated stripper
shoe/mold assembly in accordance with one embodiment of the claimed
invention.
FIG. 2 comprises a perspective view of the heated stripper
shoe/mold assembly depicted in FIG. 1.
FIG. 3 is a top plan view of the heated stripper shoe depicted in
FIG. 1.
FIG. 4 depicts a partial cross-sectional view of the heated
stripper shoe shown in FIG. 2.
FIG. 5 is a top plan view of the mold depicted in FIG. 1.
FIG. 6 is a perspective view of a concrete masonry block made in
accordance with the embodiment of the claimed invention shown in
FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention comprises a heated stripper shoe, a heated stripper
shoe/mold assembly and a method of forming concrete masonry blocks
with the shoe and mold assembly.
THE STRIPPER SHOE/MOLD ASSEMBLY
Turning to the Figures wherein like parts are designated with like
numerals throughout the several views, FIG. 1 shows a stripper shoe
and mold assembly 8. The stripper shoe and mold assembly generally
includes a stripper shoe plate 30, having a lower side 33 and an
upper side 35. The stripper shoe plate 30 may have indentations to
form block edges or details such as those shown at 31 on the shoe
lower side 33, see also FIG. 2. Heat blocks 32 may be positioned on
the stripper shoe plate upper side 35. Heat elements 34 may be
positioned or inserted within the heat blocks 32.
Positioned over the heat blocks 32 on the upper surface of the shoe
plate is a heat shroud 40. The heat shroud 40 has a lower side 43
and an upper side 45. The heat shroud lower side 43 has
indentations 42 positioned to cover the heat blocks 32 once the
heat shroud 40 is positioned over the upper surface 35 of the
stripper shoe plate 30, (see also FIG. 4).
Also shown in FIG. 1 is the standoff 50 which attaches the stripper
shoe assembly 8 to the block machine head (not shown). The standoff
50 is capable of spacing the stripper shoe plate 30 appropriately
in the block machine and insulating the head from the heat
developed at the surface of the stripper shoe plate 30.
The assembly also comprises a mold 20 having an interior perimeter
designed to complement the outer perimeter of the stripper shoe
plate 30. The mold generally has an open center 25 bordered by the
mold walls. In fact, the mold may take any number of forms or
embodiments such as those depicted in U.S. Pat. No. 5,062,610,
incorporated herein by reference
Positioned beneath the mold is a pallet 10 used to contain the
concrete fill in the mold and transport finished blocks from the
molding machine. The stripper shoe assembly 8 may be seen in FIG. 2
in its assembled form.
The stripper shoe 30 serves as a substrate on which the heat
elements 34 and heat blocks 32 are contained. Further, the stripper
shoe plate 30 also functions to form the body of the block as well
as detail in the blocks through indentations in the stripper shoe
lower surface 33, see FIG. 4. In use, the stripper shoe 30
functions to compress fill positioned in the mold and, once formed,
push or strip the block from the mold 20.
The stripper shoe plate 30 may take any number of designs or forms
including ornamentation or structural features consistent with the
block to be formed within the mold. Any number of steel alloys may
be used in fabrication of the stripper shoe as long as these steel
alloys have sufficient resilience and hardness to resist abrasives
often used in concrete fill. Preferably, the stripper shoe 30 is
made from steel alloys which will resist continued compression and
maintain machine tolerances while also transmitting heat from the
heat elements through the plate 30 to the fill. In this manner, the
total thermal effect of the heat elements is realized within the
concrete mix.
Preferably, the stripper shoe plate 30 is made from a carbonized
steel which may further be heat treated after forging. Preferred
metals include steel alloys having a Rockwell "C"-Scale rating from
about 60-65 which provide optimal wear resistance and the preferred
rigidity. Generally, metals also found useful include high grade
carbon steel of 41-40 AISI (high nickel content, prehardened
steel), carbon steel 40-50 (having added nickel) and the like. A
preferred material includes carbon steel having a structural ASTM
of A36. Preferred steels also include A513 or A500 tubing, ASTM
42-40 (prehardened on a Rockwell C Scale to 20 thousandths of an
inch). The stripper shoe plate may be formed and attached to the
head assembly by any number of processes known to those of skill in
the art including the nut, (36A-36D), washer (57), and bolt 56A-56D
mechanism shown in FIG. 1.
One preferred heated stripper shoe design which complements a two
block mold is shown in FIG. 1. Sides 37 and 39 of the stripper shoe
have an indentation 31 on the shoe lower side 33. A heat block 32
is positioned over both indentations 31. The outer perimeter of the
stripper shoe 30 may generally complement the interior outline of
the mold 20. Heat blocks 32 are preferably positioned adjacent to
each indentation 31 on the shoe lower side 33 to facilitate the
formation of that point of detail created by the indentation 31 in
the stripper shoe 30. While generally shown with one form of
indentation 31, the stripper shoe plate 30 may be capable of
forming any number of designs through indentations in the shoe
plate lower surface 33 depending on the nature of the block to be
formed.
The invention may also comprise one or more heat elements 34, FIG.
1. Generally, the heat element 34 functions to generate and
transmit radiant energy to the upper surface 35 of the stripper
shoe 30. The heat elements are preferably positioned adjacent
indentation 31 in the shoe plate lower surface 33.
Generally, any number of heat elements 34 may be used in accordance
with the invention. However, preferred heat elements have been
found to be those which will withstand the heavy vibration, dirt
and dust common in this environment. Preferred heat elements are
those which are easily introduced and removed from the system. This
allows for easy servicing of the stripper shoe assembly without
concerns for injury to the operator through thermal exposure or
complete disassembly of mold 20, stripper shoe 30, shroud 40, and
standoff 50.
The heat element may comprise any number of electrical resistance
elements which may be, for example, hard wired, solid state, or
semiconductor circuitry, among others. One system found preferable,
(FIGS. 1 and 3), is a cylindrical heat element 34 inserted into
fastening means such as heat block 32. This heat element 34 is
easily introduced into the heat block 32 and held in the heat block
by any number of means such as a screw, bolt, or bracket inserted
through opening 38.
In this embodiment of the invention, the heat element 34 may
generally run the length of heat block 32 and is positioned
parallel to edges 37 and 39 of the stripper shoe 30, FIG. 3. The
heat element is also positioned at the stripper shoe upper surface
35 preferably adjacent the indentations 31 formed in the sides 37
and 39 of the stripper shoe 30 at its lower surface 33. By this
positioning, the heat element 34 is able to apply heat to the
stripper shoe 30 in the area where it is most needed, that is,
where the block detail (in this case, flange 62, see FIG. 6) is
formed in the concrete mix held by the mold.
The heat element 34 may comprise any number of commercially
available elements. Generally, the power provided by the heat
element may range anywhere from 300 watts up to that required by
the given application. Preferably, the power requirements of the
heat element may range from about 400 watts to 1500 watts, more
preferably 450 watts to 750 watts, and most preferably about 600
watts. Power may be provided to the heat elements by any number of
power sources including for example, 110 volt sources equipped with
20 to 25 amp circuit breakers which allow the assembly to run off
of normal residential current. If available, the assembly may also
run off of power sources such as 3-phase, 220 volt sources equipped
with 50 amp circuit breakers or other power sources known to those
of skill in the art. However, the otherwise low power requirements
of the assembly allow use in any environment with minimal power
supplies.
Elements found useful in the invention include cartridge heaters,
available from Vulcan Electric Company, through distributor such as
Granger Industrial Co. of Minnesota. These elements have all been
found to provide easy assembly and disassembly in the stripper shoe
of the invention as well as good tolerance to vibration, dirt,
dust, and other stresses encountered in such an environment.
Generally, the heat elements may be activated by hard wiring 70,
FIGS. 1 and 3, as well as any other variety of electrical feeds
known to those of skill in the art. If hard wiring is used
provision may be made to circulate this wiring 70 through the
shroud 40 and standoff 50 by various openings 48 and 58,
respectively. The heat element 34 may be externally controlled
through any number of digital or analogue mechanisms known to those
of skill in the art located at an external point on the block
machine.
The invention may also comprise means of attaching the heat element
34 to the stripper shoe 30 such as heat block 32, FIG. 1. In a
preferred embodiment of the invention, the heat block 32 also
contains the heat generated by the heat element 34 from the head
assembly and directs that heat energy towards the stripper shoe
30.
In accordance with these functions, the heat block 32 disclosed
herein may take any number of shapes or forms and comprise any
number of different materials. Preferably, the heat block 32 may be
designed to provide a highly serviceable releasable containment
area for the heat element 34. The heat block may be positioned on
the upper surface 35 of the stripper shoe 30 adjacent any
corresponding area of detail on the lower surface 33 of the
stripper shoe 30.
In one embodiment of the invention, the heat block 32 preferably
takes the shape of a three dimensional rectangle having a square
cross section, FIGS. 1, 3 and 4. The heat block 32 may be hollowed
or bored out to allow insertion of a heat element 34 into the block
32. The heat block 32 may also have any number of holes or
apertures useful in the insertion of screws, bolts, or other means
useful holding the heat element 34 within the block 32.
Generally, the heat block 32 may be held on the stripper shoe by
any number of means including welding, bolting and the like. As can
be seen in FIG. 4, the heat block 32 may have any variety of cross
sectional shapes including that of a square or rectangle. Once the
heat element 34 is placed into the heat block 32, wiring may be
played out from the heat element and inserted through the heat
shroud 40 and head standoff 50 to the appropriate connection at the
top of the head.
The heat block 32 may comprise any number of materials which allow
for the releasable fixing of the block 32 and heat element 34 to
the shoe 30. Preferably, the heat block 32 has an open bottom which
allows the element 34 to lie flush and in contact with the stripper
shoe upper surface 35. This configuration allows free transmission
of heat to the upper surface of the stripper shoe while precluding
or insulating the head structure from the heat generated by the
heat element 34.
Generally, the heat block may comprise any number of metal alloys
including ASTM 41-40 carbon steel, and A36 cold roller steel, hot
rolled carbon steel. The preferred metal has been found to be A36
cold rolled steel due to its low conduction of heat which thereby
further thermally insulates the shroud 40 and standoff 50.
The stripper shoe may also comprise a heat shroud 40, FIG. 1, which
thermally shields or insulates the head standoff 50 and molding
machine. The heat shroud 40 also functions to focus the heat
generated by the heat elements back onto the stripper shoe 30.
The heat shroud 40 may take any number of shapes of varying size in
accordance with the invention. The heat shroud 40 should preferably
contain the heat elements 34. To this end, the heat shroud 40
preferably has a void 42 formed within its volume so that it may be
placed over the heat block 32 positioned on the upper surface 35 of
the stripper shoe 30. At the same time, the shroud 40 is preferably
positioned flush with the stripper shoe upper surface 35.
Preferably, there is a space 41, FIG. 4, between the upper surface
of the heat block 32 and the opening or void in the heat shroud 40.
Air in this additional space 41 also serves to insulate the
standoff and mold machine from the heat created by the heat element
34 contained within the block 32.
Generally, the heat shroud 40 may comprise any metal alloy
insulative to heat or which is a poor conductor of thermal energy.
Metal alloys such as brass, copper, or composites thereof are all
useful in forming the heat shroud 40. Also useful are aluminum and
its oxides and alloys. Alloys and oxides of aluminum are preferred
in the formation of the heat shroud 40 due to the ready commercial
availability of these compounds. Aluminum alloys having an ASTM
rating of 6061-T6 and 6063-T52 are generally preferred over
elemental aluminum.
The assembly may additionally comprise a head standoff 50, FIG. 1,
to position, aid in compression, and attach the head assembly to
the block machine.
Generally, the head standoff 50 may comprise any number of designs
to assist and serve this purpose. The head standoff may also be
used to contain and store various wiring or other elements of the
stripper shoe assembly which are not easily housed either on the
stripper shoe 30, or the heat shroud 40.
The head standoff 50 may comprise any number of metal alloys which
will withstand the environmental stresses of block molded
processes. Preferred metals include steel alloys having a Rockwell
"C"-Scale rating from about 60-65 which provide optimal wear
resistance and the preferred rigidity.
Generally, metals found useful in the manufacture of the head
standoff mold of the present invention include high grade carbon
steel of 41-40 AISI (high nickel content, prehardened steel),
carbon steel 40-50 (having added nickel) and the like. A preferred
material includes carbon steel having a structural ASTM of A36.
Generally, the head standoff 50 may be made through any number of
mechanisms known to those of skill in the art.
Preferably, the standoff has an open design allowing for quick
dissipation of heat. One preferred form of the head standoff 50 can
be seen in FIGS. 1 and 2. In this embodiment the standoff has holes
58 for receipt of the studs 36A-36D stemming from the stripper shoe
plate 30. Opening 58 allows for the further stringing of wiring 70
stemming from the heat elements 34. The standoff 50 may be further
attached to the block machine through openings 55 in the top plate
54 of the standoff 50.
As can be seen in FIGS. 1, 2 and 5, the invention may also comprise
a mold 20. The mold generally functions to facilitate the formation
of the blocks. Accordingly, the mold may comprise any material
which will withstand the pressure to be applied to the block filled
by the head. Preferably, metal such as steel alloys having a
Rockwell "C"-Scale rating from about 60-65 which provide optimal
wear resistance and the preferred rigidity.
Generally, other metals found useful in the manufacture of the mold
of the present invention include high grade carbon steel of 41-40
AISI (high nickel content, prehardened steel), carbon steel 40-50
(having added nickel) and the like. A preferred material includes
carbon steel having a structural ASTM of A36.
Mold 20 useful in the invention may take any number of shapes
depending on the shape of the block to be formed and be made by any
number of means known to those of skill in the art. Generally, the
mold is produced by cutting the steel stock, patterning the cut
steel, providing an initial weld to the pattern mold pieces and
heat treating the mold. Heat treating generally may take place at
temperatures ranging from about 1000.degree. F. to about
1400.degree. F. from 4 to 10 hours depending on the ability of the
steel to withstand processing and not distort or warp. After heat
treating, final welds are then applied to the pieces of the
mold.
Turning to the individual elements of the mold, the mold walls
generally function according to their form by withstanding the
pressure created by the press. Further, the walls measure the
height and the depth of resulting blocks. The mold walls must be
made of a thickness which will accommodate the processing
parameters of the block formation given a specific mold
composition. Preferably, the mold walls range in thickness from
about 3/8 inch to about 1 inch, preferably from about 1/2 inch to
about 3/4 inch.
In one preferred embodiment of the invention, FIGS. 1, 2 and 5 the
mold may be fitted to form two blocks comprising four walls and an
open central cavity 25, FIG. 5. The four walls are generally a
front wall 21, a back or rear wall 3, and first and second opposing
sidewalls, 22 and 24. Flanges such as 26-29 FIG. 5, may be formed
on the interior sides of the mold walls to form ornamental features
in the blocks or assist in forming splitting points for blocks that
are formed in tandem or "siamese".
BLOCK MOLDING
In operation, the assembly 8 is generally positioned in the block
molding machine atop of a removable or slidable pallet 10, FIGS. 1
and 2. The mold 20 is then loaded with block mix or fill. As
configured in FIGS. 2 and 5, the mold 20 is set to form two blocks
simultaneously in a "siamese" pattern. Once formed and cured, these
blocks may be split along an edge created by flanges which may be
positioned on the interior of sidewalls 22 and 24 generally along
axis A'-A, FIG. 5. Prior to compression, the upper surface of the
mold is vibrated to settle the fill and scraped or raked with the
feed box drawer (not shown) to remove any excess fill. The mold is
then subjected to compression directly by the stripper shoe 30
through head assembly 8.
Upon compression, the stripper shoe 30 forces block fill towards
either end of the mold into the stripper shoe indentation 31 to
create a flange 62 in the formed block 60, FIG. 6. This flange may
range in size for example from about 3/8" to 2", preferably about
2/3" to 11/2", and most preferably about 2/4" to 11/4".
In accordance with the invention, this indentation 31 is heated by
element 34 contained in the heat block 32 so that flanges of
minimal size and varying shape may be formed without the build up
of fill on the stripper shoe 30 at indentation 31. By doing so, the
assembly may be used in the automatic manufacture of blocks by
machine.
Blocks may be designed around any number of different physical
properties in accordance with ASTM Standards depending upon the
ultimate application for the block. For example, the fill may
comprise from 75 to 95% aggregate being sand and gravel in varying
ratios depending upon the physical characteristics which the
finished block is intended to exhibit. The fill generally also
comprises some type of cement at a concentration ranging from 4% to
10%. Other constituents may then be added to the fill at various
trace levels in order to provide blocks having the intended
physical characteristics.
Generally, once determined the fill constituents may be mixed by
combining the aggregate, the sand and rock in the mixer followed by
the cement. After one to two and one-half minutes, any plasticizers
that will be used are added. Water is then introduced into the fill
in pulses over a one to two minute period. The concentration of
water in the mix may be monitored electrically by noting the
electrical resistance of the mix at various times during the
process. While the amount of water may vary from one fill
formulation to another fill formulation, it generally ranges from
about 1% to about 6%.
Once the mold has been filled, leveled by means such as a feed box
drawer, and agitated, a compression mechanism such as a head
carrying the inventive assembly converges on the exposed surface of
the fill. The stripper shoe assembly 30 acts to compress the fill
within the mold for a period of time sufficient to form a solid
contiguous product. Generally, the compression time may be anywhere
from 0.5 to 4 seconds and more preferably about 1.5 to 2 seconds.
The compression pressure applied to the head ranges from about 1000
to about 8000 psi and preferably is about 4000 psi.
Once the compression period is over, the stripper shoe 30 in
combination with the underlying pallet 10 acts to strip the blocks
60 from the mold 20. At this point in time the blocks are formed.
Any block machine known to those of skill in the art may be used in
accordance with the invention. One machine which has been found
useful in the formation of blocks is a Besser V-3/12 block
machine.
Generally, during or prior to compression the mold may be vibrated.
The fill is transported from the mixer to a hopper which then fills
the mold 20. The mold is then agitated for up to 2 to 3 seconds,
the time necessary to ensure he fill has uniformly spread
throughout the mold. The blocks are then formed by compressive
action by the compressive action the head. Additionally, this
vibrating may occur in concert with the compressive action of the
head onto the fill in the mold. At this time, the mold will be
vibrated for the time in which the head is compressed onto the
fill.
Once the blocks are formed, they may be cured through any means
known to those with skill in the art. Curing mechanisms such as
simple air curing, autoclaving, steam curing or mist curing, are
all useful methods of curing the block of the present invention.
Air curing simply entails placing the blocks in an environment
where they will be cured by open air over time. Autoclaving entails
placing the blocks in a pressurized chamber at an elevated
temperature for a certain period of time. The pressure in the
chamber is then increased by creating a steady mist in the chamber.
After curing is complete, the pressure is released from the chamber
which in turns draws the moisture from the blocks.
Another means for curing blocks is by steam. The chamber
temperature is slowly increased over two to three hours and then
stabilized during the fourth hour. The steam is gradually shut down
and the blocks are held at the eventual temperature, generally
around 120.degree.-200.degree. F. for two to three hours. The heat
is then turned off and the blocks are allowed to cool. In all
instances, the blocks are generally allowed to sit for 12 to 24
hours before being stacked or stored. Critical to curing operations
is a slow increase in temperature. If the temperature is increased
too quickly, the blocks may "case-harden". Case hardening occurs
when the outer shell of the block hardens and cures while the inner
region of the block remains uncured and moist. While any of these
curing mechanisms will work, the preferred mechanism is
autoclaving.
Once cured the blocks may be split if they have been cast "siamese"
or in pairs. Splitting means which may be used in the invention
include manual chisel and hammer as well as machines known to those
with skill in the art. Splitting economizes the production of
blocks of the present invention by allowing the casting of more
than one block at any given time.
In one preferred embodiment of the invention, a block 60 such as
that shown in FIG. 6 is cast in pairs, joined at surface 64. The
block is formed top side 68 down with flange 62 directed upwards
and positioned at either end of the mold 20 at sides 21 and 23, see
FIG. 5. When cast in pairs, the blocks 60 may be cast to have
indentations or groove created by flanges 26-29 on their side
surfaces between the two blocks. Flanges may also be positioned on
the interior of the mold side walls to provide a natural weak point
or fault which facilitates the splitting action when positioned
along axis A'-A. The blocks may be split in a manner which provides
a front surface 64 which is smooth or coarse, single faceted or
multifaceted, as well as planar or curved. Preferably, splitting
will be completed by an automatic hydraulic splitter. When split,
the blocks may be cubed and stored.
The above discussion, examples and embodiments illustrate our
current understanding of the invention. However, since many
variations of the invention can be made without departing from the
spirit and scope of the invention, the invention resides wholly in
the claims hereafter appended.
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